JP6401246B2 - Corona igniter with hermetic combustion seal - Google Patents

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority based on US Provisional Application Serial No. 61/8199098, filed May 3, 2013, the entire disclosure of which is hereby incorporated by reference. Be considered and incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona igniter for ionizing a fuel-air mixture to form a corona discharge by emitting a high frequency electric field and a method for forming the igniter.

Related Art A corona ignition system includes an igniter having a central electrode that is charged to a high frequency high voltage potential and generates a strong high frequency electric field in a combustion chamber. This electric field promotes combustion of the fuel-air mixture by ionizing a portion of the fuel-air mixture in the combustion chamber and initiating breakdown. Preferably, the electric field is controlled so that the fuel-air mixture produces a corona discharge, also called non-thermal plasma, while maintaining dielectric properties. The ionized portion of the fuel-air mixture forms a flame front, which then becomes self-supporting and burns the remaining portion of the fuel-air mixture. Preferably, the electric field is controlled so that the fuel-air mixture does not lose all dielectric properties. This creates a thermal plasma and an electric arc between the electrode and the grounded cylinder wall, piston or other part of the igniter. An example of a corona discharge ignition system is disclosed in US Pat. No. 6,883,507 to Freen.

  A corona igniter is typically formed from a conductive material and includes a central electrode for ionizing the fuel-air mixture by receiving a high frequency high voltage and emitting a high frequency electric field into the combustion chamber to form a corona discharge. The electrode typically includes a high voltage corona enhancing electrode tip that emits an electric field. An insulator formed from an electrically insulating material is disposed around the center electrode. The ignition device also includes a metal shell that houses the center electrode and the insulator. However, the igniter does not include any grounded electrode elements that are intentionally placed in close proximity to the ignition end of the center electrode. Instead, grounding is preferably provided by the cylinder wall or piston of the ignition system. An example of a corona igniter is disclosed in US Patent Application Publication No. 2012/0210968 by Lykowski et al.

  As shown in FIG. 1 of Patent Application Publication No. 2012/0210968, the metal gasket forms a seal along the folded area of the shell and insulator. However, over time, mechanical and thermal stresses wear the gasket. Thus, the gasket cannot ensure a hermetic seal over the entire service life of the ignition device. In addition, the metal gasket cannot prevent air from entering the gap between the shell and the insulator through the bottom opening of the shell, and thus can cause the formation of a corona discharge in the gap. In order to prevent the formation of corona discharge in the gap, a filler material such as a resin can be placed between the shell and the insulator. However, filling materials tend to degrade over time because they are exposed to harsh conditions during engine operation.

SUMMARY OF THE INVENTION One aspect of the present invention provides a corona igniter that includes a center electrode, an insulator, and a metal shell. The central electrode receives a high frequency voltage and emits a high frequency electric field, thereby ionizing the fuel-air mixture and forming a corona discharge. The shell is formed from metal and surrounds the center electrode. Further, the shell extends in the longitudinal direction from the upper end of the shell to the lower end of the shell along the central axis. The insulator and the shell form a gap extending in the longitudinal direction along the central axis between the insulator and the shell. The ceramic combustion seal seals the gap between the insulator and the shell.

  Another aspect of the present invention provides a method of forming a corona igniter. The method includes the step of receiving a high frequency voltage and emitting a high frequency electric field to ionize the fuel-air mixture and form a central electrode for forming a corona discharge. The method also includes placing a center electrode in the lumen of the insulator. The insulator extends longitudinally along the central axis and includes an insulating nose region. Further, the method uses a shell formed from metal and extending longitudinally from the top of the shell to the bottom of the shell, the insulator nose region extending outside the bottom of the shell, and the insulator and shell are both Enclosing the insulator so as to form a gap therebetween. The gap extends longitudinally along the central axis. The method also includes sealing the gap by placing a ceramic combustion seal between the insulator and the shell.

  The ceramic combustion seal protects the gap from combustion gases and protects any filler material that may be placed in the gap. In addition, ceramic combustion seals are durable and do not cause significant mechanical or thermal stress, so they can operate well over the service life of the corona igniter.

  Other advantages of the present invention will become readily apparent as will be better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings.

1 is a cross-sectional view of a corona igniter including a ceramic combustion seal in the form of a bush, in accordance with an exemplary embodiment. 2 is an enlarged view of a portion of FIG. 1 showing a ceramic combustion seal between an insulator and a shell. FIG. 3 is a cross-sectional view of a corona igniter including a ceramic combustion seal in the form of a cylinder, according to another exemplary embodiment. FIG. 3 is an enlarged view of a portion of FIG. 2 showing a ceramic combustion seal between the insulator and the shell. FIG. 3 is a cross-sectional view of a corona igniter including a ceramic combustion seal in the form of a ring, according to another exemplary embodiment. FIG. 4 is an enlarged view of a portion of FIG. 3 showing a ceramic combustion seal between the insulator and the shell. FIG. 6 is a cross-sectional view illustrating a corona igniter including a ceramic combustion seal disposed along a lower shell end according to another exemplary embodiment. FIG. 5 is an enlarged view of a portion of FIG. 4 showing a ceramic combustion seal between the insulator and the shell. FIG. 6 is a cross-sectional view of a corona igniter prior to mounting a ceramic combustion seal between a metal shell and an insulator, according to another exemplary embodiment. FIG. 6 is a cross-sectional view of a corona igniter including an insulator of a different design than the insulators of FIGS. FIG. 5 is a cross-sectional view of a comparative corona igniter including a copper ring disposed in the insulator groove and brazed to the insulator and metal shell to seal the gap.

DETAILED DESCRIPTION An exemplary embodiment of a corona igniter 20 according to the present invention is shown in FIGS. 1-6, and a comparative corona igniter is shown in FIG. Corona igniter 20 includes a center electrode 22 for receiving a high radio frequency voltage, an insulator 24 surrounding the center electrode 22, and a metal shell 26 surrounding the insulator 24. The center electrode 22 includes a corona augmentation tip 28 for ionizing the fuel-air mixture by emitting a high frequency electric field and forming a corona discharge. The ceramic combustion seal 30 attaches the insulator 24 to the metal shell 26 and hermetically seals the gap 32 between the insulator 24 and the metal shell 26. The ceramic combustion seal 30 prevents combustion gases from entering the gap 32 that can adversely affect the performance or service life of the corona igniter 20. The ceramic combustion seal 30 also protects any filler material 34 that may be placed in the gap 32.

  The center electrode 22 of the corona igniter 20 is formed from a conductive material to receive a high frequency voltage, typically a peak-to-peak voltage in the range of 20-75 KV. The center electrode 22 emits a high-frequency electric field generally in the range of 0.9 to 1.1 MHz. The center electrode 22 extends in the longitudinal direction from the terminal end 36 to the electrode ignition end 38 along the center axis A. The center electrode 22 includes a corona augmentation tip 28 generally provided at the electrode ignition end 38. As shown in FIGS. 1-6, the tip 28 includes, for example, a plurality of prongs.

  The insulator 24 of the corona igniter 20 is formed from an electrically insulating material such as alumina. The insulator 24 includes an insulator surface 40 that surrounds the lumen, houses the center electrode 22, and extends longitudinally along the center axis A from the insulator top end 42 to the insulator nose end 44. Generally, the center electrode 22 and the electrical contact are fixed to the lumen of the insulator 24 using a seal. The insulator 24 also includes an insulator outer surface 46 that defines an insulator outer diameter Di and extends longitudinally from the insulator upper end 42 to the insulator nose end 44. As shown in FIGS. 1 to 6, the insulator 24 includes an insulator nose region 48, and the insulator outer diameter Di gradually decreases toward the insulator nose end 44 along the insulator nose region 48. Generally, the electrode ignition end 38 is disposed outside the insulator nose end 44. The insulator outer surface 46 in the embodiment of FIGS. 1-6 includes a groove as a stress concentrating portion for holding the ceramic combustion seal 30, like the insulator of the comparative ignition device shown in FIG. 7. Not in.

  In the exemplary embodiment of FIGS. 1-6, the insulator outer diameter Di decreases along the portion of the insulator 24 toward the insulator nose end 44 to form an insulator lower shoulder 49, The insulator upper shoulder 62 is formed by decreasing along the part of the insulator 24 toward the insulator upper end 42 at a position away from the insulator lower shoulder 49. In the embodiment of FIGS. 1-5, the insulator outer diameter Di is constant between the insulator lower shoulder 49 and the insulator nose region 48 along a portion of the insulator 24. Alternatively, however, the insulator outer diameter Di may vary between the insulator lower shoulder 49 and the insulator nose region 48 along a portion of the insulator 24. In the embodiment of FIG. 6, the insulator outer diameter Di decreases toward the insulator nose region 48 to form a second insulator lower shoulder 49. The insulator outer diameter Di between the second insulator lower shoulder 49 and the insulator nose end 44 is generally the insulator outer diameter between the insulator lower shoulder 49 and the insulator upper shoulder 62. It is smaller than Di. In general, the insulator outer diameter Di gradually decreases along the insulator nose region 48 to the insulator nose end 44.

  The shell 26 is made of a metal material such as steel and surrounds at least a part of the insulator 24. The shell 26 extends along the central axis A from the shell upper end 50 to the shell lower end 52. The shell 26 includes a shell outer surface 54 and a shell inner surface 56. The shell inner surface 56 faces the central axis A and extends from the shell upper end 50 to the shell lower end 52 along the insulator outer surface 46. The shell inner surface 56 forms a lumen surrounding the central axis A and a shell inner diameter Ds extending perpendicularly across the central axis A. Shell inner surface 56 also forms a shoulder for engagement with shoulders 49 and 62. In the embodiment of FIG. 6, the shell 26 includes an inner rib 64 for engaging the lowest of the two insulator lower shoulders 49. The shell inner diameter Ds is generally greater than or equal to the insulator outer diameter Di along the entire length of the insulator 24 from the insulator upper end 42 to the insulator nose end 44 so that the corona ignition device 20 can be assembled in the forward direction. is there. The term “assemble in the forward direction” means that the insulator nose end 44 is inserted into the shell lumen through the shell upper end 50 rather than the shell lower end 52. However, in an alternative embodiment, along part of the length of the insulator 24, it is less than or equal to the insulator outer diameter Di, thus assembling the corona igniter 20 in the reverse direction. The term “reverse assembly” means inserting the insulator nose end 44 through the shell lower end 52 into the shell lumen. The embodiment of FIGS. 1-6 shows the corona igniter 20 assembled in the forward direction, with an insulator nose region 48 extending outside the shell lower end 52. However, the present invention can be used with corona igniters assembled in the opposite direction or with other designs. In the exemplary embodiment of FIGS. 1-5, the shell 26 is formed around the shoulders 49, 62 of the insulator 24, and the shell upper end 50 is located on the insulator upper shoulder 62. In the embodiment of FIG. 6, the shell upper end 50 extends longitudinally beyond the insulator upper end 42.

  A gap 32 between the insulator 24 and the shell 26 generally extends along the central axis A from the shell lower end 52 to the insulator lower shoulder 49 adjacent to the return region of the ignition device 20 in the longitudinal direction. . The gap 32 extends radially outward from the insulator outer surface 46 to the shell inner surface 56 with respect to the central axis A. In the embodiment of FIGS. 1 and 2, the shell inner diameter Ds increases in the vicinity of the shell lower end 52 to increase a portion of the gap 32. The increased portion of the gap 32 holds the ceramic combustion seal 30.

  Stabilizing the corona igniter 20 by compressing a conformal element 58, such as a soft metal gasket formed from copper or annealed steel or plastic material or rubber material, between the metal shell 26 and the insulator 24. be able to. The conformal element 58 is located at a position spaced longitudinally from the ceramic combustion seal 30. Thus, the conformal element 58 forms another seal between the insulator 24 and the shell 26 and closes the end of the gap 32. FIGS. 1-6 illustrate a conformal element 58 in the form of a gasket disposed between the shoulders 49, 62 of the insulator 24 and the metal shell 26. 1-5, the gasket is disposed between the insulator lower shoulder 49 and the metal shell 26. FIG. 5 also shows a second gasket disposed between the insulator upper shoulder 62 and the shell upper end 50. In FIG. 6, the gasket is only disposed between the insulator upper shoulder 62 and the metal shell 26.

  Once the insulator 24 is placed in the metal shell 26, a gap 32 is formed between the insulator outer surface 46 and the shell inner surface 56. During engine operation, air or other gas from the combustion chamber enters the gap 32 and forms a corona discharge in the gap 32, reducing the intensity of the corona discharge at the electrode ignition end 38. Is not desirable. As shown in FIGS. 3A and 4A, in many cases, filling gap 34 with filler material 34 prevents the formation of corona discharge. However, the filler material 34 can degrade over time when exposed to combustion gases.

  As shown in FIGS. 1-6, the ceramic combustion seal 30 is positioned along the gap 32 between the shell 26 and the insulator 24 to prevent air from entering the gap 32 or from combustion gases. The filling material 34 is protected. The ceramic combustion seal 30 extends continuously from the metal shell 26 to the insulator outer surface 46, thus forming a hermetic seal between the insulator 24 and the shell 26. As shown in FIGS. 1-6, the ceramic combustion seal 30 preferably extends from the shell lower end 52 or from the shell inner surface 56 adjacent to the shell lower end 52 to the insulator outer surface 46 adjacent to the insulator nose region 48. Extend. The ceramic combustion seal 30 is formed from a sintered ceramic material such as alumina. The ceramic combustion seal can be formed from a sintered ceramic material that is the same as or different from the material from which the insulator is formed. The ceramic combustion seal 30 is also preferably a durable element such as a non-hollow bush, cylinder or ring, but may have a variety of different shapes. The outer surface of the ceramic combustion seal 30 that engages the shell 26 and the insulator 24 is generally flat and engages the flat surfaces 46, 52, 56 of the insulator 24 and / or the shell 26.

  The ceramic combustion seal 30 is first placed along the gap 32 and then attached to the insulator 24 and shell 26. As shown in FIGS. 1A and 2A, a ceramic combustion seal 30 is typically bonded to the insulator 24 and shell 26 using a glass material or glass / ceramic mixture 60. The glass material consists essentially of glass and the glass / ceramic mixture comprises any proportion of glass and ceramic mixture. However, in another embodiment, as shown in FIGS. 3A and 4A, the ceramic combustion seal 30 is brazed to the metal shell 26 and then the insulator 24 using a glass material or glass / ceramic mixture 60. Mounted.

  In the embodiment of FIGS. 1 and 1A, the ceramic combustion seal 30 is a bushing disposed between the insulator 24 and the shell 26. Since the shell inner diameter Ds increases in the vicinity of the shell lower end 52, the shell inner surface 56 forms a groove for accommodating the bush. The bush includes a cylindrical portion disposed along a portion of the shell inner surface 56 having an increased shell inner diameter Ds. The bush also includes a convex edge portion extending outward from the cylindrical portion to the shell outer surface 54 along the shell lower end 52. The cylindrical portion and the convex edge portion of the bush extend along the insulator outer surface 46 and are directly adjacent to the insulator nose region 48.

  In the embodiment of FIGS. 2 and 2A, the ceramic combustion seal 30 is a cylinder disposed within the gap 32. Similarly, the shell inner surface 56 has an increased shell inner diameter Ds, and the cylinder is positioned along the increased shell inner diameter Ds. The cylinder extends along the shell inner surface 56 slightly beyond the shell lower end 52, but does not extend along the shell lower end 52. The cylinder also extends along the insulator outer surface 46 and is directly adjacent to the insulator nose region 48.

  In the embodiment of FIGS. 3 and 3A, the ceramic combustion seal 30 is a ring disposed within the gap 32. The ring has a rectangular cross section. In this embodiment, the shell inner surface 56 does not have a groove. Instead, the ring extends along the shell lower end 52 from the shell outer surface 54 to the insulator outer surface 46 adjacent to the insulator nose region 48. Also in the embodiment of FIGS. 3 and 3A, the filler material 34 is disposed in the gap 32 between the insulator 24 and the shell 26.

  In the embodiment of FIGS. 4 and 4A, similarly, the ceramic combustion seal 30 extends along the shell lower end 52 from the shell outer surface 54 to the insulator outer surface 46, and the filler material 34 is the insulator 24. And in the gap 32 between the shell 26. However, in this embodiment, the ceramic combustion seal 30 has a triangular cross section.

  Another aspect of the present invention provides a method of forming a corona igniter 20. The method includes placing the center electrode 22 on the insulator 24 and placing the insulator 24 on the metal shell 26 using either a forward assembly process or a reverse assembly process. The method further includes forming a ceramic combustion seal 30 from a sintered ceramic material such as alumina. The ceramic combustion seal 30 is preferably a bush, cylinder or ring, but may have a variety of different shapes. FIG. 5 shows the corona igniter 20 before the ceramic combustion seal 30 is installed between the insulator 24 and the shell 26.

  The method then places the ceramic combustion seal 30 along the gap 32 and attaches the ceramic combustion seal 30 to the shell 26 to form a hermetic seal between the insulator 24 and the shell 26. Process. The attaching process generally includes bonding the ceramic combustion seal 30 to the insulator 24 and shell 26 using a glass material or glass / ceramic mixture 60. In another embodiment, the method includes brazing the ceramic combustion seal 30 to the metal shell 26 and bonding the ceramic combustion seal 30 to the insulator 24 using a glass material or glass / ceramic mixture 60.

  FIG. 7 shows a corona ignition device 120 of a comparative example. The corona igniter 120 of the comparative example includes a copper ring 130 disposed in a groove in the insulator 124 adjacent to the insulator nose region 148 to form a seal between the insulator 124 and the shell 126. However, since the groove provided in the insulator 124 generates a large concentrated stress, the insulator 124 may be cracked over time. Traditionally, solid glass fillers have been used to seal the gap between the igniter insulator and the shell, but solid glass fillers tend to corrode over time when exposed to combustion gases. There is.

  The corona igniter 20 with the ceramic combustion seal 30 of the present invention extends the useful life of the corona igniter 20 compared to an igniter that uses other components to seal the gap between the insulator and the shell. Are expected to function better. The ceramic combustion seal 30 is durable and does not cause significant mechanical or thermal stress, so it can operate well over the service life of the corona igniter.

  Obviously, many modifications and variations of the present invention are possible in light of the above teachings, and may be practiced otherwise than as specifically described in the claims.

Claims (19)

A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
Formed of metal, surrounding the centric electrode, a shell which extends longitudinally from the shell top to the shell bottom along the center axis,
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
Ceramic combustion seal, to seal the gap between said insulator shell,
The ceramic combustion seal is a corona igniter formed from a sintered ceramic material . The corona igniter of claim 1 , wherein the sintered ceramic material of the ceramic combustion seal comprises alumina. The ceramic combustion seal extends continuously from the shell lower end and / or inner shell surface near the shell lower end across the gap to the insulator;
The corona igniter of claim 1, wherein the ceramic combustion seal hermetically seals the gap. The shell includes a shell inner surface facing the insulator and has a shell inner diameter extending perpendicularly across the central axis;
The shell inner diameter increases near the lower end of the shell,
The corona igniter of claim 1, wherein the ceramic combustion seal is disposed in the gap along the increased shell inner diameter near the shell lower end. The corona igniter of claim 4 , wherein the ceramic combustion seal includes a cylindrical portion disposed within the gap along the increased shell inner diameter. A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
A shell formed of metal and surrounding the central electrode and extending longitudinally from the upper end of the shell to the lower end of the shell along the central axis;
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
A ceramic combustion seal seals the gap between the insulator and the shell ;
The shell includes a shell inner surface facing the insulator and has a shell inner diameter extending perpendicularly across the central axis;
The shell inner diameter increases near the lower end of the shell,
The ceramic combustion seal is disposed in the gap along the increased shell inner diameter near the shell lower end ;
The ceramic combustion seal includes a cylindrical portion disposed within the gap along the increased shell inner diameter ;
The ceramic combustion seal is a bushing including the cylindrical portion disposed in the gap along the increased shell inner diameter;
The said bush is a corona ignition device containing the convex edge part extended outside from the said cylindrical part along the said shell lower end. A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
A shell formed of metal and surrounding the central electrode and extending longitudinally from the upper end of the shell to the lower end of the shell along the central axis;
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
A ceramic combustion seal seals the gap between the insulator and the shell ;
The ceramic combustion seal comprises a corona igniter including a ring disposed along the lower end of the shell. A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
A shell formed of metal and surrounding the central electrode and extending longitudinally from the upper end of the shell to the lower end of the shell along the central axis;
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
A ceramic combustion seal seals the gap between the insulator and the shell ;
The corona igniter wherein the ceramic combustion seal is bonded to at least one of the insulator and the shell by a glass material or a mixture of glass and ceramic. A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
A shell formed of metal and surrounding the central electrode and extending longitudinally from the upper end of the shell to the lower end of the shell along the central axis;
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
A ceramic combustion seal seals the gap between the insulator and the shell ;
A corona igniter wherein the ceramic combustion seal is brazed to the shell. The insulator comprises an insulator outer surface having an insulator outer diameter extending perpendicularly across the central axis;
The insulator outer surface extends in the longitudinal direction from the insulator upper end to the insulator nose end,
The outer diameter of the insulator decreases along the part of the insulator toward the insulator nose end to form an insulator lower shoulder,
The outer diameter of the insulator decreases along the part of the insulator toward the upper end of the insulator at a position away from the lower shoulder of the insulator, thereby forming an upper shoulder of the insulator;
The insulator outer diameter gradually decreases along the insulator nose region toward the insulator nose end;
The insulator outer diameter between the insulator lower shoulder and the insulator nose end is smaller than the insulator outer diameter between the insulator lower shoulder and the insulator upper shoulder,
The upper end of the shell is disposed on the upper shoulder of the insulator,
The corona igniter of claim 1, wherein the ceramic combustion seal is disposed along a portion of the insulator outer surface between the insulator lower shoulder and the insulator nose region. The corona igniter includes at least one conformal element disposed within the gap and compressed between the insulator and the shell;
The corona igniter of claim 1, wherein the conformal element is spaced apart from the ceramic combustion seal along a longitudinal direction.   The corona igniter of claim 1, comprising a filler material that fills at least a portion of the gap between the insulator and the shell. A corona ignition device,
A central electrode for receiving a high frequency voltage and ionizing the fuel-air mixture by emitting a high frequency electric field to form a corona discharge;
A shell formed of metal and surrounding the central electrode and extending longitudinally from the upper end of the shell to the lower end of the shell along the central axis;
An insulator disposed between the central electrode and the shell;
The insulator extends in the longitudinal direction along the central axis, and includes an insulator nose region extending outside the lower end of the shell;
The insulator and the shell form a gap therebetween, the gap extending longitudinally along the central axis;
A ceramic combustion seal seals the gap between the insulator and the shell ;
The center electrode is disposed so as to extend in a longitudinal direction from a terminal end to an ignition end along the central axis,
The ignition end of the central electrode includes a corona augmenting tip disposed on the axially outer side of the insulator nose region, and has a plurality of prongs extending respectively radially outward from the central axis;
The insulator extends in a longitudinal direction from an insulator top end to an insulator nose region, the insulator nose region adjacent to the insulator nose end;
The insulator comprises an insulator surface surrounding a lumen that receives the center electrode and extending longitudinally from the insulator top to the insulator nose end;
The insulator comprises an insulator outer surface having an insulator outer diameter extending perpendicularly across the central axis;
The insulator outer surface extends in a longitudinal direction from the insulator top end to the insulator nose end,
The outer diameter of the insulator decreases along the part of the insulator toward the insulator nose end to form an insulator lower shoulder,
The outer diameter of the insulator decreases along the part of the insulator toward the upper end of the insulator at a position away from the lower shoulder of the insulator, thereby forming an upper shoulder of the insulator;
The insulator outer diameter gradually decreases along the insulator nose region toward the insulator nose end;
The insulator outer diameter between the insulator lower shoulder and the insulator nose end is smaller than the insulator outer diameter between the insulator lower shoulder and the insulator upper shoulder,
The insulator upper shoulder engages the shell upper end;
The insulator is formed of alumina;
The central electrode is secured to the insulator surface by a conductive seal;
The shell includes a shell outer surface surrounding the insulator outer surface and facing the insulator outer surface, and a shell inner surface facing the insulator outer surface away from the insulator outer surface,
The shell inner surface and the shell outer surface extend in the longitudinal direction from the shell upper end to the shell lower end along the central axis,
The inner shell surface defines a lumen for receiving the central electrode and a shell inner diameter extending perpendicularly across the central axis;
The shell inner diameter is greater than the insulator outer diameter along the length of the shell,
The gap between the insulator and the shell extends in a radial direction from the insulator outer surface to the shell inner surface with respect to the central axis,
The gap between the insulator and the shell extends in the longitudinal direction from the insulator lower shoulder to the shell lower end along the central axis,
At least one conformal element is disposed in the gap, compressed between the insulator outer surface and the shell inner surface, and spaced longitudinally from the ceramic combustion seal;
The at least one conformal element seals the gap at a location spaced longitudinally from the ceramic combustion seal;
One of the at least one conformal elements is disposed between the insulator lower shoulder and the inner shell surface;
One of the at least one conformal elements is a gasket formed from metal, rubber material or plastic material;
A filler material is disposed in the gap between the ceramic combustion seal and the conformal element;
The ceramic combustion seal extends continuously from the shell lower end and / or a shell inner surface near the shell lower end across the gap to the insulator, hermetically sealing the gap;
The ceramic combustion seal is formed from a sintered ceramic material;
The sintered ceramic material of the ceramic combustion seal comprises alumina;
The ceramic combustion seal is formed as a bush, cylinder or ring;
The corona igniter wherein the ceramic combustion seal is bonded to at least one of the insulator and the shell by a glass material or a mixture of glass and ceramic. It said ceramic combustion seal, along said shell lower end or adjacent to arranged cylinders, including a bush or ring, corona ignition device according to claim 1 3. Wherein one of the at least one conformal element, the is compressed between the insulator upper shoulder portion and the shell surface, corona ignition device according to claim 1 3. A method of forming a corona igniter comprising:
Receiving a high frequency voltage and emitting a high frequency electric field to ionize the fuel-air mixture and form a central electrode for forming a corona discharge;
Disposing the center electrode in a lumen of the insulator, the insulator extending longitudinally along a central axis and including an insulating nose region;
Using a shell formed of metal and extending in the longitudinal direction from the upper end of the shell to the lower end of the shell, the insulator nose region extends outside the lower end of the shell, and the insulator and the shell are between them. Surrounding the insulator to form a gap, the gap extending longitudinally along the central axis,
Sealing the gap by placing a ceramic combustion seal comprised of a sintered ceramic material between the insulator and the shell. The method of claim 16 , comprising inserting the insulator nose region into the shell lumen through the shell top. A method of forming a corona igniter comprising:
Receiving a high frequency voltage and emitting a high frequency electric field to ionize the fuel-air mixture and form a central electrode for forming a corona discharge;
Disposing the center electrode in a lumen of the insulator, the insulator extending longitudinally along a central axis and including an insulating nose region;
Using a shell formed of metal and extending in the longitudinal direction from the upper end of the shell to the lower end of the shell, the insulator nose region extends outside the lower end of the shell, and the insulator and the shell are between them. Surrounding the insulator to form a gap, the gap extending longitudinally along the central axis,
Providing a ceramic combustion seal between the insulator and the shell to seal the gap;
Wherein the step of sealing, with a mixture of glass material or glass ceramic, comprising the steps of adhering to at least one of the ceramic combustion seal between the insulator and the shell, the method. A method of forming a corona igniter comprising:
Receiving a high frequency voltage and emitting a high frequency electric field to ionize the fuel-air mixture and form a central electrode for forming a corona discharge;
Disposing the center electrode in a lumen of the insulator, the insulator extending longitudinally along a central axis and including an insulating nose region;
Using a shell formed of metal and extending in the longitudinal direction from the upper end of the shell to the lower end of the shell, the insulator nose region extends outside the lower end of the shell, and the insulator and the shell are between them. Surrounding the insulator to form a gap, the gap extending longitudinally along the central axis,
Providing a ceramic combustion seal between the insulator and the shell to seal the gap;
It said step of sealing comprises a wax contact step the ceramic combustion seal the shell method.

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